160818542-dental-decks-radiology-2011-2012

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RADIOLOGY Digital Rad

Which tlTe of digital image receptor is most common at tlris time?

(Charge Injection Device)(Complementarv Metal Oxide Seniconductor/Atiive Pixel Sensor)

(Charge-Coupled Device)

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are required lbr direct digital image producrion. These components include an x-rayan elecffonic snsor, a digitil interface card, a computer with an analog-to-digilal con\efter lADC). a

monitor, sofhvarc, and a printer Tlpically, systcms are PC based *ith a 486 or higher proccssor, 640intemal memory cquipped .|.t'ith an SVCA graphics card, and a high-resolution monitor /1024 X 768 pi*Direci digital senso$ are eilher a charge-cotlplcd device /Ca'D) or complemenlary metal oxide semicon-pixel sensot (CMOS-APS).CCD is thc most common device used today.The CCD is a solid-state detcctor composed ofan anay of

sensitive pixels on a pure silicon chip. A pixel or picture element consisN of a small electroninto which thc x-ray or light energy is deposited upon exposure. The individual CCD pixel size is ap-40I wilh thc latest versious in the 20F range. Thc rows ofpixels are rrranged in a matrix of 5I2pixels. Charge coupling is a process whereby the numbcr ofclcctrons deposited in cach pixel are trans-one well 1{) thc next in a sequential manner to r rcad-out amplifier filr imagc display on the mon-

are tuo typcs ofdigital sensor array designs: area and linar. Arr arrays are used tbr intraorllwhile linear arrays are used in extraor|l imsging. Area arrays are available iD sizes compara-size 0, size l, and size 2 film. but the sensors are rigid and thickcr than radiographic film and have a

area for image capture. The sensor communicates with the computcr through all electricalcomplementary metal oxide smiconductor active pixl sensor fa'ryo.t-.4PS/ is the latest development

sensor technology. Externally. CMOS sertsors appcar idcntical to CCD dctectors but lhey useaclive pixel technology and are lss expensive to manufacturc. Thc APS technology rsduces by a factor ofthe system power required to process the image conpared with the CCD. In addition. rhe APS systemthe nccd for charge transf'er and may improvc the reliabilify and lifespan ofthe sensor. In sum-

CMOS sensors have scvcral advantages including design integration, low power requrremenls. mimu_and low cost. Horvever, CMOS scnsors have more fired pattern noise and a smaller rctivefor image acquisition.

injection device or CID is another sensor technology used in dental digital radiograph). A CIDsilicon-bascd solid-state imaging rcceptor much like the CCD. Structurally, howevcr, the CID differs fromCCD. No computer is required to process lhe images. This system features a CID x-ray sensor. cord, and

that are insc(cd into the light source on a camera platform; digital images are seen on the system moni-within seconds.


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gray-scale resolutionexposure to x-radiation

speed of image viewingequipment and film costs

efficiencyeducation tool

ofdiagnostic imageCop).dght O 201 I -20 l2 - Dental Decls

Indirect digital imagingirect digital imaging

Storage phosphor imaging

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or electronic imaging has bccn availablc lbr morc lhan a dccadc. lt is cslinatcd that l0-207o ofdcntal prac-usc digital imaging tcchnology in thcir dcntal practicc. It is anticipatcd thcsc numbers will steadily increasc

thc ncxt fivc to tcn ycars as dcntistry continucs to movc from film bascd to digital inraging. Film-based imag-consists ofx-ray inieraction with clcctrons in thc lilm cmulsion. production ofa lalcnl inragc, and chcnrical pro-

that transfoffns thc latcnt imagc into a visible onc.fi1m providcs a mcdium for rccording. displayiDg, and sloring diaeirrosiic infbrmation. Film-

inragcs arc dcscribcd as analog images. Analog imagcs arc charactcrizcd by continuous shadcs ofgray liomarca to the next betwccn thc cxtrcmcs ofblack and \lhitc. Each shadc ofgray has an optical dcltrsity klarknet,

to lhe amount oflight that can pass through thc imagc ai a spccific silc. Film displays higher resolution thanrcccpfors wilh a rcsolving powcr ofabout l6lplmm (lnrcs puirs/nil/td"/"r'l. However, tilm is a rclativcly in-radiation deiector ard, thus, rcquircs rclatively high radiation cxposurc.Thc usc oircctangular collimationthc highest speed lilm arc mcthods thal rcducc rudiation cxposurc. Chcmicals ar(} nccded to process the image

arc olicn drc sourcc of crrors and rctakcs. Thc finalresult is a fixcd nnagc that is dillicult lo manipulalc oncc cap-imaging is thc rcsult of x-ray intcrrction *ith clectrons in clectronic sensor pirels fpi./ru e ?l?nents), cotr-ofanalog data to digital data, computcr proccssing, and display ofihc visiblc imagc on a computcr scrccn.

acquircd by thc scnsor is communicatcd to the conputcr in analog tbmr. Computcrs opcraic on thc binary num-systcm in which hvo digits /0 dr./ // arc uscd to rcprcscnt data. Thcsc two charactcrs arc callcd bits (bi ar) digit),thcy form words eight or morc bits in lcngth c^llcd bytes. Thc total nunrbcr ofpossible bylcs for 8-bit languagc= 256. Thc analog-tc.digital converter translbrms analog data into numcrical dala bascd on thc binary num-systcm. Thc vohagc of thc output signal is nrcasurcd and assigncd a numbcr trom 0 fbld.t/ to 255 (\'hit?) ac-to thc intcnsity ofthc voltagc. Thcsc numcrical assignmcnts translatc into 256 shades of gra!. Thc humanis ablc to detect approximatcly 32 gray lcvcls.

has dislinct advantagcs ovcr lilnt in Icrms ofcxposurc rcduclion, climlnation ofprocessinginslanr or rcal timc imagc production and display. imagc cnhanccmcnt, paticnt educatjon utility, and con-

amount ofcxposurc rcduction is dcpcndent on a numbcr offactors including film spccd.arca. collimation. and relakcs. Thc primary disadvantages includc drc rigidily and thickncss ofthc sensor,

rcsolution. highcr inilial systcm cost, unknown scnsor lifcspan. and pcrfccl scm iconduc tor chargc Iransfir.Infection controlprcscnts anolhcr chal lcngc forclinicians using dircct digitalimaging. CCD scnsors cannol bcCarc nccds to bc tak.n to propcrly prcparc, covcr, and cnsurc thc barrier is nol damagcd during paticnt im-proccdurcs. Dircct saliva contact with thc rcccptor and clcctrical cablc must bc avoidcd to p.cvcnt crossconta-

methods of obtaining a digital image currently exist: direct digital imaging, indirectimaging, and storage phosphor imaging.

. To produce a direct digital x-ray image, three components are necessary: an x-ray machine,an intraonl sensor, and a computer monitor The images are captured using a solid-state de-tector or sensor such as a charge-coupled device {CCDJ, a complementary metal oxide semi-conductor/active pixel sensor (CMOS / AP.S/. or a charge injection device /C/Dl. The sensorthen transmits the image to a computer monitor Within seconds of exposing the sensor tox-rays. an image appears on the computer screen. Software is then used to enhance andstore the image.. The essential components ofan indirect digital imaging system include a CCD camera andcomputer. In this method, an existing x-my film is "digitized" using a CCD camera. TheCCD camera scans the image, digitizcs or converts the image, and then displays it on thecomputer momtor. A third method ofobtaining a digital image is storage phosphor imaging, a wireless dig-ital radiography system. In this system, a reusable imaging plate coated with phosphorsis used instead of a sensor with a fiber optic cable. The plates are described as "wireless"because they are not connected via cable or wire to the computer. The plates are similar inevery way to conventional intraorul film, including size, thickness, rigidity and placement.These plates store the energy from incoming x-rays, and are then placed in a scanning de-vice. The scanner stimulates the stored x-ray infonnation by subjecting the plate to a laserlight. When the light strikes the phosphor material, energy is released as a light signal in anelectronic waveform and is converted to a digital image by the computer. The image can notinstantaneously be viewed on the monitor, but takes from 30 seconds to 5.5 ninutes de-pending upon the system and certain variables.


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RADIOLOGY Dig Rad

You have a patient who is extrmly concerned about the radiationerposure he will receive when he gets intraoral pictures taken. You lethim know that if he wants the least exposure then you will use:

Digital radiographyE-speed filmsF-speed filmsPanoramic instead ofa full mouth series

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ofthe positive features ofdigital radiography is that it requires less radiation than con-radiography, because the sensor is more sensitive to x-rays than dental frlm. Ex-

times for digital radiography are from 507o to 80%o shorter than those lor E-speedand about 50% shoter than those of F-sneed hlm. This translates into less radiation

for the patient... L All direct and PSP digital radiography systems use a conventional dental x-liotce:' ray unit. The literature emphasizes that the x-ray unit must have the ability to

reduce exposure times to 0.01 seconds to reduce the likelihood of oversaturat-ing the sensor.2. In digital radiography, a sensoq or small detector is placed inside the mouthofthe patient to capture the radiographic image. The sensor is used instead ofintraolal film. As in conventional radiography the x-ray beam is aimed to strikethe sensor An electronic charge is produced on the surface of the sensori thiselectronic signal is digitized, or converted into "digital" fom.r.3. Digital radiography systems are not limited to intraoral images; panoramicand cephalometric images rray also be obtained.

The intase magnification on a dental x_ray is influenced bv the:' TarqeFfifm dist^nce (a!ro La\etl sorrLel,-/irm distdn.e) is thc distance bctween the source or-r-raysUo.al \pot on the tungsten target) and the film lr is dercrmincd by the length ofrhe posirion_indicating dc_,. :c rtl:o ttlletl ptD). When a longer pID is used, more parallei ra1,s ir; rhc middle ofrhe x-ray bicanri:-r.h :he object rather than thc diverging x_rays from the pcriphcry olthe beam. As a resuft, a tonger plI)::i :ir{eafilm distance result in less image magnillcetion. ond a shortcr pID and target-tilo distance re_j.i.: l: more image magnification.' object-film distanc: is the distance berween_the object bcing rrdiographed /r7 r.ro1[/ and rhc x-ray:i T Thc closer rhe proximiry ofrhe toorh 10 rhc film. fie less ima-ge enligcml;t thcre _;tt bc on the film.\ decrease In objecl_frrn' distance rcsurts in a decrease in magnitication, an_d an increase in objec!firm dis_.::r:c:esulti ln an increas in imagc magnification.image does not have the same size and shape as the object being radiographed. A dimensionalofa radiographic image is influenced by:alignment:10 minimize dimensionaldistortion the film and should be parallel to the longis ofthc rooth. Foreshortening rcsultsfrom excessive verti{:al angulation when the x-ray bcarn is perlto rhe film but not thc toorh. Elongation resolrs \rhen the x-ray bearn is oricnred at righl an_to the tooth but not to thc film.\-rai besm: to minimiTe dimensional disro(ion, the x-ray beam musr be directed perpendicurar !o rhe

and rhe film.ofcontrast: is rhe range ot'usefur densitics secn on a dentar radiograph.Tu,o rcrms arc usd ro dcscribeppearance ofan x-ray:short-scal contrast: is an x-ray that shows only tno densities. areds olblack and white. short_scale con_results lionl the usc ofa lor{,er kilovoltage range.Long-scrle contrast: is an x-ray that shows many densities, or nany shades ot gray. Long_scale con_results from the usc ofa higher kilovotage range.

is thc difrercnce in degrccs ofbrackncss bct*een adiacsnt areas on an x-ray. Low contrast describeswrth many shades ofgray and few areas ofblack and white. High contra;t describcs an x_ray withblack and white areas and ferv shades ofqray.


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sinus space

patientdentiststate

ofthe above

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structures/materials:. Less radiation penetrates the structure and reaches the film. Radiopaque structures appear white on the processed film. Dense materials such as metals. enamel. dentin. and bonestructures/materials:

. Allow radiation to pass through, absorbing very little. More radiation penetrates the structure and reaches the film. Radiolucent structures appear gray to black on processed filfir

. Less dense materials, including soft tissue and air spaceRadiographs show shading from black to white fr?os/ radiolucent to most ra-Example: Least to most radiopaque: periodontal ligament space, dentin,

ZOE. amalsam.

Dental radiographs should be kept indefinitel"v.dental record must include documentation of informed consent and the exposure of(e.g., the number and type of .filn.s, the rationale./or exposure and the

tiotl). Legally, dental radiographs are the property of the dntist. Patients do,have a right to reasonable access to the dental radiographs, which includesa copy ofthe radiographs forwarded to another dentist.

Patients may refuse dental x-rays, howeveq the dentist must decide whether an ac-can be provided and whether treatment can providec.document can be signed by the patient that releases the dentist from

Based on the orientation ofthe embossed d,ot (i(lenti/ication dot), there aremethods ofmounting radiographs: labial mounting fi, ilh the raised or convex side oJ

dot;facing the vieu'erl and lingual m o.|[]'ting (with the depressed or concave tide oJ theJacing the vielr,er/. The labial mounting method is recommended by the AmericanNote: With the labial mounting method, the radiographs are viewedifthe viewer is looking directly at the patient; that is, with the right quadrants in the leftof the film mount and those ofthe left quadrants in the risht side ofthe film mount.


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Your dental hygienht has a patient who states that she needs bite.wingx-rays because it has been six months since the last nlms were taken.Your hygienist should respond in which manner listed below?

Agree with the patientTell the patient that bite-wing x-rays should be taken once a yearTell the patient that dental x-rays are taken only when needed as judged by eachpatient's needsNone ofthe above

8Copyrighr O 2011,2012 , Denral Decks

Identify the structure below that the arnows are pointing to:

Reprirted fronHaring. Joenlannucc' andLauraJansen: Dentrl Rrdiography:Principles and Techniqles:Thnd Edilion. O:000, wirh permission fron Elsevier.

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about the number, t)?e and frequency ofdental x-rays are determind by thebased on each patient's needs. Every patient has a different dental condition andthe frequency of x-rays is different as well. There are guidelines published by the

that aid a dentist in prescribing the number, type and frequency of dental x-rays.Patients who have tooth decay, periodontal disease, tooth mobility, pain in one or

teeth or possible impacted teeth need more frequent radiographic examinationspatients without such problems. Remember: For a pediatric patient who is caries(and asy-mptomatic). the first bite-wing radiographs should not be taken until thebetween the posterior teeth have closed.

Occult diseases (/br example, small carious lesions, .!-sts qnd tumors) are thoseno clinical signs or symptoms, Because occult disease in the perioral tissues

(except Jbr caries), a radiographic examination of the jaws should not be un-solely to look for it in an individual with teeth when there are no clinical signssymptoms. However, every x-ray taken should be evaluated for these lesions.

Caries is an exception to the above rule because ofits much higher preva-as comnared to occult cvsts or tumors.

hamulus lalso known as the hamular proc'ess.) is a srnall hook-like projection olbonefrom the medial pterygoid plate ofthe sphenoid bone. The hamulus is locatedto the maxillary tuberosity region.

the radiograph its image is seen in proximity to the posterior surface ofthe tuberositymaxilla. It varies greatly in length, width and shape from patient to patient. It usu-exhibits a bulbous point, but sometimes the point is tapered.

The maxillary tuberosity appears as a radiopaque bulge distal to the third molar region

Reprinred from Haring, Joen Iannucciand LauraJansen: DentalRadrography:Prin'ciples and Techniques: Ttird Edilion. o 2000. *ith pemission from Ekevir


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RADIOLOGY NormalAnatThe image ofthe coronoid process of the mandible oftenappears in periapicrl x-rrys o{:

he incisor region ofthe mandiblemolar region of the mandible

region ofthe maxillamolar region of the maxilla

10Coplaight ie 20ll-201: - DeDtal Decks

NormalAnat

Identify eech structure that the arrows 1-8 pointto in the anterior region ofthe maxilla.

''Cornesy Dr Sluan C. $'l'ne, UCLA SchooloiDenrisfy.'11

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the mouth is opened, the process moves forward, and therefore it comes into r iewoften when the mouth is opened to its fullest extent at the time the exposure is made.is evidenced by a tapered or triangular radiopacity, which may be seen below, or in

instances, superirrposed on the molar teeth and maxilla.

The coronoid process appears as a triangular-shaped radiopacit_v.Repnnred liom H.nDg. Joen Iannuccilnd L.ura Jansen Lind: Rldiograph'cIfrenretdtio ior tlle Dent.l l lr-gienr \r. 10 199.1- sitir permissioi frcn El!e!rer

The opaqu lin -+ Lateral wall ofnasopalatine canal (inci.sive canal)The opaque line -) Anterior wall of maxillary sinus'Ihe radiolucent structure -) Nasopalatine lossaThe opaque line -) Floor ofnasal fossaThe opaque structur -+ Soft tissue tip ofnoseThe opaque line -) Lamrna duraThe opaque line -+ Border ofrnaxillary sinusThe radiolucent line -+ Periodontal ligament space


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NormalAnat

Identify each structure that the rrrows l-7point to in th anterior region ofthe

''Counesy Dr. Stuan C. Whi1e. UCLA School of Denrisrry "12

CopyriShr lil20ll'?01: ' DenEl Decks

Identify each structure that the .rrows l-5point to in the mandibular molar region.

"Coudesy Dr. Stuan C. wlrire, UCLA School of Denrirry. '13

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The opaque structur + Anterior nasal spineThe opaque line -t Lateral wall ofnasopalatine canalThe radiolucent lin -+ Intermaxillary sutureThe opaque llne + Floor ofnasal fossaThe radlolucent structure + Incisive/l.,lasopalatine foramenThe rediopaque line -+ Soft tissue tip ofnoseThe oprque structure -t Alveolar crest

The radiopaque linss + Nutrient canalThe opaque line -t Bony trabecular plateTh oprque line + Inferior border ofrnandibular canalThe radiolucent space + Submandibular gland fossaThe radlopaque structure + Inferior border ofmandible


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NormalAnat

Identify each structure that the arrows 1-8point to in the maxillary molar region.

"Counesy Dr Stuart C. Whire. UCLA School ofDenrisrrv ''t4

Coplrighr r.!' 201 l-l0l: - Denral Dccks

RADIOLOGY

Identify each structure that the arrows I -7poina to in the mandibular incisor region.

"Counesy Dr Sruan C. Whne. UCI-A School ofDcntistry. '15

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The opaque line + Anterior wall ofmaxillary sinusThe opaque mass + Inferior conchaThe opaque lin + Floor ofnasal fossaThe opaque line + Inferior border ofzygomatic process ofmaxillaThe opaque line + Posterior wall ofzygomatic process ofmaxillaThe opaque line + Inferior border of zygoma (zygomatic arch)The opaque line + Floor ofmaxillary sinusThe opaque structure + Mucosa over maxillary alveolar ridge

The opaque structure + Lingual cusp of lst premolarThe radiolucent line -+ Periodontal ligament spaceThe opaque mass + Film holderThe opaque mass -+ Genial tuberclesThe radlolucent circle + Lingual foramenThe opaqneline -) Bony trabecular plateThe radlolucent sprce -t Marrow space


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Identify each structure that the arrows 1--4point to in the mandibular premolar region.

"Courtesy Dr Snran C. wltite. UCLA School of Denlistry"16

Copy ighr C 2011,2012 - Dental Decks

Identify each structure that the rrrows 1-3point to in the msndibular premolar rsgion.

''Counesy Dr Stuan C. Write, UCLA School of Dentisrry "Copyrighr C 20ll-2012 - Dental Decks


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The radiolucent line -+ Periodontal lisament sDaceThe radiolucent space -) Mental foramenLarge radiolucent space -+ Submandibular gland fossaDark dot -+ Film clin mark

The opaque line -) Cemento-enameljunctionThe radiolucent space -+ Mental foramenLarge radiolucent space -> Submandibular gland fossa


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Identify each structure that th arrows 1-7point to in the maxillary premolar region,

''Coudesy Dr Stuan C. \lhne, UCI-A School of Denrisln."18

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}IOLOGY

Identify each structure that the arrows 1-6point to in the maxillary canine region.

''Counesy Dr Stuart C. White, UCLA School of Denrisrry. '19CoplriShr lO 201 1,2012, Den6l Decks


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The opaque mrss -+ Inferior conchaThe opaque line -) Anterior wall ofmaxillary sinus

+ Floor ofnasal fossaThe radlolucent space + Maxillary sinusThe opaque line -+ Floor ofmaxillary sinusThe opaque structure + Inferior border ofzygomatic process ofthe maxillaThe opaque llne + Lingual cusp offirst premolar

The opaque line -+ Floor ofnasal fossaThe opaque line -) Lateral wall in nasopalatine canalThe opaque line + Ala ofnoseThe oprque line -) Anterior wall ofmaxillary sinusThe radiolucent space -t Maxillary sinusThe oprque line + Lingual cusp of lst premolar


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RADIOLOGY NormalAnat

Identify each structure that the arrows 1-6point to in the maxillary molar region.

''Counesl Dr Stuan C. Whire, UCLA SchoolofDenrsln.20

Copvrighl C 20ll ?01: Denr.l Dects


Identify each structure that the arrows 1-3point to in the mandibular incisor region.

''Coudes) Dr Sruan C. w]rne, UCLA S.hool of Dentinry "Copyrighr rr 20ll-l0l: - Denlal Dccks


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The opaque line -+ DEJThe lucent line -+ Periodontal ligament spaceThe opaque line -+ Lamina duraThe lucent line -> Periodontal ligament space ofpalatal rootThe opaque spot -+ Film holderThe opaque region -+ Mucosa over maxillary ridge

The radiopaque masses --> Mandibular toriThe radiolucent circl -+ Lingual foramenThe radiopaque mass -+ Genial tubercles


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Identify each structure that the arrows 1-4point to in the mandibular incisor/canine region.

''Councsy Dr Sruart C. Wh're. UCI-A SchooIoIDcntistry.'Copyrighr ill 20ll l012 DenralDectr


Identify each structure that the arrows 1-8point to in the maxillary incisor region.

*Counesy Dr. Stuart C whrte. UCLA School ofDenristry.23

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The radiopaque structure + Alveolar crstThe radiopaque line + Lamina duraThe radlolucent line + Periodontal ligament spaceThe radiopaque line + Bony trabecular plate

The radlolucent spsce -t Marrow spaceThe radiolucent line + Periodontal ligament spaceThe radiopaque llne + Bony t'abecular plateThe rrdiopoque line -l Lamina duraThe lucent line -+ Pulp canalThe opaque structure -+ Alveolar crestThe opaque structure -) Dentin (root)The opaque structure + Enamel ofsrown


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RADIOLOGY NormalAnatldentify each structure that the arrows l-9point to in the maxillary incisor region,

"Counesy D' Sruan C. Whire. UCI-A School of Dcnrisrry24Coplright r.!l20ll-20ll - Dental Dccks


Identify each structure that the arrows 1-12point to in the maxillary canine region,

''Counesy Dr Stuan C. Whre. UCLA School ofDentistry.-25

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The opaque materiol + DentinThe rsdiolucent line + Bony tabecular plateThe radlolucent space -t Bony marrow spacThe lucent structure + Pulp canalThe lucent line -+ Periodontal ligament spaceThe opeque line + Lamina dumThe oplque structure -+ Alveolar crestThe oprque structure -) EnanelThe lucent structure + Pulp chamber

The opaque line + Trabecular plateThe lucent sprce -t Marrow spaceTooth numbr? + l0The opaque line + Larnina duxaThe opaque materhl -+ DentinThe radiolucent llne + Periodontal ligament spaceThe opaque structure + Alveolar crestThe radiolucent structure + Pulp canalThe radiolucent structure + Pulp chamber

The opaque mtterid + EnamelThe oprque clrcle + Premolar buccal cusp over raised film dotThe opaque line -+ DEI


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NormalAnat

Identify each structure that the arrows 1-8point to in th maxillary premolar region.

''Courtesv Dr Stuan C. Whire. UCLA School o i Dent istry."CoDrighr al:0ll ?012 Denral Decks

NormalAnat

Identify each structur that the arrows 1-15point to in the partial panorex.

C. While, UCLA

CopyriShr i.] 20ll 2012 ' Denral Decks


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Tooth number? -+ 3material is this? -+ Silver amalgam

Whrt ls thls oprcity? + Plastic bite blockThe black dot + Film dotThe black marks + PLS for Kodak Ektaspeed plus filmThe opaque line + Lamina duraThe lucent line + Periodontal ligament spaceThe opaque llne + Lamina dura

The lucent sprce -) Air in nasal fossaThe opaque line + Nasal septumThe opaque line + Lateral wall ofnasal foss4 medial wall ofmaxillary sinusThe opaque line + Infrao6ital rimThe opaque line + Border ofinfraorbital canalThe radiolucent space + Pterygomaxillary fissureThe opaque line + Pterygoid spine ofsphenoid boneThe opaque mass + Zygomatic archThe oprque line + Posterior wall of maxllla (maxillary sinus)

The oprque line + Posterior wall of zygomatic process of maxillaThe opaque mass + Ear lobeThe oprque llne + Inferior border ofmandibular canalThe opaque rnsss + Anterior nasal spineThe opaque line + lnferior border ofmandibleThe oprquc msss -) Hyoid bone


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Identify each structure that th arrows 1-13point to in the partial panorex.

The first statement is true; the second statement is falseThe first statement is false; the second statement is trueBoth statements are trueBoth statements are thlse

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C. while. UCLA

The pattern of stored energy on an exposed film is trmed tbe latent image;this image remains invisible until it undergoes processingA chemical solution known as the developer is used in the developmentprocess to chemically reduce ths exposed, energized silver halide crvstatsto trlack metallic silver.

C.t\ric rr ' -'nll l0 I Dcnr,l DeLrr

RADIOLOGY


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The opacity -> Tipof noseThe opaque line -+ Hard palate/floor ofnasal fossaThe lucent area -+ OrbitThe opaque lineThe opaque line

Hard palate/floor ofnasal fossaFloor of n.raxillary sinus

The opaque structure -+ Soft palateThe radiolucent space -+ Air between the soft palate and the dorsum of tongueThe opaque line -+ Dorsum oftongueThe opaque line (dots) -+ Shadow of opposite mandible (re.ferred to as ghost image)

The lucent oval -+ Mental foramenThe diffuse opacity -+ Shadow ofcervical spineThe broad lucency -+ Submandibular gland fossaThe opacity -+ Articular tubercle

purpose oflilm processing is trlofoldi. To conven thc latent (invisible) imagc on the film into a visible imagc -der'eloping proccss. To presene the visiblc image so that it is pemanent and docs not disappear tiom the dental x-rayfi\ing process

a bcam ofphotons exposes an x-ray film, it chemically changes thc photosensitivc siher halidein the film emulsion lldtent image). Important: Exposed arcas will becomc radiolucent,nonexposed areas will become radiopaque.

developing solution contains the following:.,\ developing agent, such as hydroquinone, which is a chemical compound that is capablc ofchang-ing the exposed silvcr halide crystals to black mctallic silvcr. At the same time, it produces no appre-ciablc cffcct on thc unexposed silver halidc crystals in the emulsion. Gives detail to the x-ray image.Note: Elon, also kno\r'n as metal, acts quickly to produce a visible radiographic inage. It scncraicsthe many shadcs of gray.. An lntioxidant preserrativ, for example. sodium sulfite, prevents the developer solution from ox-idizing in the presencc ofair.. An accelerator an alkalt (sodium carbonate) activates thc dcveloping agents and maintains thealkalinity ofthe developer at the correct value. It softens geiatin ofcmulsion.. A restrainer, such as potassium bromide, is added to dcvclopcrs to conffol the action ofthe dev-eloping agent so that it does not develop the uncxposcd silvcr halide crystals to prodrtce fog.optimal iemperature for thc dcvcloper solution is 68oF.

The function ofdeveloping solution is to remove the ha)idc portion ofthc enposed, ener-silver halide crystals to black rnctallic silver, this is refened to as reduction. The developer solu-

softcns the film emulsion during this proccss. The function offixing solution is lo stop developmcntremove remaining unenergized, unexposed silvcr halide crystals ftom the film emulsion. The fixer

thc film emulsion during thc proccss.processing involves the following 5 steps:( I ) immerse film in developer (2) rinse film in water bathdilutes lhe de*loper slott,ing the development process br removing lhe alkali accelerllor, Pre-neutralizution ofthe acidfxer) (3) immerse film in fixcr (4) q'ash film in watcr bath and (5) dryfilm.


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Which ingredient of lixer solution fuDctions to remove ill unerposed andunderdweloped silver halide crystals from the trlm emulsion?

agent

agent

30Coplright O 20ll-2012 Dental Deck5

ecrease the temperature ofthe developing solutionncrease the temperature ofthe developing solution

developing solutionmA setting

the kvp setting

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fixing solrtion conlains thc following:. Thc fixing agent f. /e.7rirg ager, is madc upofsodium thiosulfate orammonium thiosulfate and is commonlycalled hwo. The purposc ofthc fixing agcnt is to remove or clear all unerposed and underdveloped silverhalide crystrls liom thc film emulsion. Thc chcmical "clcars" thc film so that thc black silver rmagc produccd bythe dcvclopcr bccomcs distinctly pcrccptiblc. whcn the film is impropcrly cicarcd, the rcmaining unexposed sil-vcr halide crystals darkcn upon exposure to light and obscure ahe imagc.. An antioxidant preservative, thc samc prcservativc uscd in thc dcvclopcr solution. sodium sulfite, is also uscdin the fixer solution. lt prevcnts thc chcmical dctcrioration ofthc fixing aSent-. An acidifier such as acetic acid or sulfuric acid is uscd to ncufalizc thc alkaline dcvclopcr Any unncutralizcdalkali may cause the uncxposcd crltals to continue to dcvclop in thc fixcr It also produccs thc neccssary acidic cn-vironmcnt required by lhc fixing agcnt.. Thc hardener agcnt used is potassium alum, lt shrinks and hardcns thc gclatin in lhc film cmulsio affcr it hasbeen softcned by the accclcmtor in thc developing lolution. It shoflcns drying timc and protccts the cmulsion fionr

a walcr bath is used to wash the tilm.This stcp is ncccssary to thoroughly rcmovc all cxccss(i.e., thnsufaE ions atd sil\,er thiosurli?re.rnpldir, from thc cmulsio .final step in rhc film proccssing is the drying ofthc films. Iiilms nay be air-dricd at room Ienpcraturc in a dus!area or placcd in a hcated drying cabinct.

processing is a simplc mcthod uscd to dcvclop, rinsc, fix, and wash dcntal x_ray films lhc csscntial pieccrcquircd for manual proccssing is a proccssing lank, which is containcr dividcd into compartmcnts for

dcvclopcr solution, walcr bath. and fixcr solution. Notel Thc optimum tcmpcraturc lbr ihc devclopc. is bct$ccnand ?0'F, tnical timc in developer is 5 minutcs. nnsc lor 30 seconds, placc in fixcr solution for l0 minutcs and

at lcast l0 minulcs and dryprocessing is anothcr simplc way to proccss dental x-ray fillll. Thc essential piccc ofcquipmcnt required

automatic processing is thc automatic processor, which automalcs all film proccssing steps.- . 1. Fixing timc is always at lcast twice as long as thc dcvcloping limc.j\ote* 2. wirh both automalic and manual processing,8 oz. offrcsh dcvclopcr and fixcr should bc added pergallon of solution per dr].L tf u ariea radiograph werc proccsscd a sccond rime, thcrc would bc no cbangc in contmst or dcnsity.

,1. Safelighting providcs illumination in thc darkroom lo carry out proccssing activities safely withoutcxposing or damaging the film. Thc GBX-2 safelight filter by Kodak with a l5-watl bulb at lcast 4 fcctfrom thc workinq surfacc is rccommendcd.

solution gts weaker, the films will get lighter. Both the devcloping and fixing solu-should be replenished on a daily basis Remember: with both automatic and manual processing 8 oz'

fresh dcvclopcr and fixcr should be tdded per gallon of solution per da].These solutions also need to beon a regular basis, and the tanks need to be scrubbcd and cleancd as well. The following fac-affcct the life ofa developing solutionl the clcanliness ofthe tanks, the sizc ofthe films processed,

number of films processcd, and the tempcrarure ofthe solutionl. Yellowish-brown film will result from insufficient tlxing or rinsing (See Jigute #l).2. Fogged film may also result from improper film storage or outdated films.3. Low solutio levels will appear as: developcr cut-off fJll?lg, I vhile boftler SeeJigure#?or {ixer cut-offfs/rdight hlack border, Seetigure #3).4. Light spots on film may result from contact with thc fixer beforc processing (Seefgrre#1).5. Developer spots appear dark or black (See Jigure #5).

prctures .eprinFd from Hanng. Joen Iannucci and Laura Jdsen Lrnd: Rad iogrnphic Inrerprerltion for lhe Dotal Hygienisl. O 1993.pemission iom Elsevier

Fig #!


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. Aftr processing a film, you notice that is rppears too darkWhat is the most likely caused of this problem?Inadequate development timeDeveloper solution too coolDepleted developer solution

xcessive developing time

Copright O 201l-2012 DenlalDecks

cut-offcut-offfilms

electricity

Coprigh O 201 I -20 12 ' Dental Decks

A straight white border appears on the x-ray film.What is the most likely cause of this?


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- Inadequate delelopmmt time- Developer solution too cool- lnaccurate trmer or thermometer- Depleted developer solution

- Check development nme- Check developcr tcmperxrure- Replace t_aul9" timcr or lhermometer- Replenish developcr vith fiesh

Chcck dcvclopment tjme- Check developer temperaturc- Replace faulty timcr or thcnnometer' Replcnish dcveloper with fresh

- Excessive developing time- Developer solution too hot- lnaccurate timr or lhermometer- concenEated developer solution

Check tempcrature of processingsolutions and *dter brthi a!'oidSudden tmperature changebetween developer and water bath

- Exrmine film p.rckets for defects- Never unwrap films in the trcsence oflvhite lighr- Check the filter and bulb wattage ofth safe light- Check rhc darkroorn fbr light leaks- Check rhe erpiration date offillnpackages' Srorc films in a cod. dry. proiected arc!- Aroid contaminated solurions by cover-ing tanks alier each usc- Check temperature ofdeveloper

Gray: lack ofdetail - Improper safe lighting'Light leaks in dark'room- outdated fitms- Improper film storage" Contaminated solutions- Developer solulion toohot

Lxample Appearance Problems SolutionsDevelopercut-off Stmight u'hite border Underdeveloped portion offilm due to low level of

developerCheck developer levcl bcforcprocessing: add solulion ifneeded

Fixetcu!-off Straighi black border Unfixed portion offilm due tolow level offixer Chcck fixer Ievel befbrc proc-essingl add solution ifneededOverlappedfilms whitc or dark areasappear on film whereoverlapped

Two films contacing eachother during processing

Separate films so thal no contactiakes placc during processing

Airbubbles whitc spots Air trapped on ihe filmsurface after being placed inthe processing solutions

cenlly agitale film racks aftcrplacing in processrng solutionsFingemailal.ifact Black crescentshaped lnarks Film emulsion damaged bythe opemtoa's fingemail duringrough handling

cenlly handle films by the edScsonlYFingerprintartifact

Black fingcr?rint Fi:m louched by ingers thatare contaminated with fluorideor developer

Wash and dry hands thoroughlybefore processing

StaticelectricjtyThin. black, branching - occurs when film packet is

opened quickly- Occurs when film pack isopened before the radiographertouches a conduciive object

- Open film packel slowiy- Touch a conductive objectbefore unwrapping films

Scratchcdfilm Soft emulsion removed fromthe film by a shalp objecr Use care when handling filmsand film racksRqJr.rerl li.r Hrnng..loen tannu.ci and Lluri Jahen: Denlal RadDgrlphy: Pnnciples and Te.hnlques Thrd Ediri.n !' 1000. *nh

I)enni$ron from !l\e\rer


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REM

Roentgen

bone cellscells

cells

cells

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Coplright C 2011-2012 - Denral Decfts


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rad (radiotion absorbed dose) is a unit used to measure a quantity called absorbedThis relates to the amount ofenergy actually absorbed in some material, and is used

any type ofradiation and any material. One rad is defined as the absorption of 100 ergsof material. The unit rad can be used for any type of radiation, but it does notthe biological effects ofthe different radiations.(roentgen equivalent man) is a unit used to derive a quantity called equivalentThis relates the absorbed dose in human tissue to the effective biological damage

radiation. Not all radiation has the same biological effect, even for the same amountdose. Equivalent dose is often expressed in terms ofthousandths ofa rem, or

To detenrine equivalent dose (rent),yon multiply absorbed dose (rad) by a qual-factor (QF) that is unique to the type ofincident radiation. The QF is a t'actor used lorprotection purposes that accounts for the exposure effects of different types ofFor x-rays QF : 1.

roentgen is a unit used to measure a quantity called exposure. This can only be usedan amount of gamma and x-rays, and only in air

is a measure ofradiation quantity, the capacity ofthe radiation to ionize air.dose is used to compare the biologic efl'ects ofdifferent types ofradiation to

or organ.dose is used to estimate the risk in humans.

/Gr, js a unit lor measuring absorbed dose; the Sl unit equivalent to the rad: I gray100 rad.

ioniting radiation is h:rrmful and produccs chemical changes th.rt rcsults in biologic damsge in liviDg tissuc.spccific mcchanisms olradiation injury are possiblc: ionization and frec radical formation /1, is is l|rc pritnd^'

ofradialim injury:. Thc direct theort: suggcsts lhal ccll damagc rcsuhs whcn ionizirg radialion directll hits crilical arcas. or tar-!.rs. q Jlhin $c ccll. Dircct altcration ofbiologic molccrlcs (i.c., (u bohrlrat$, 14il!, prct?int, DN 1/ occuts. Appro\rrnalcl) one-third ofdrc biologic cffccls ofx-ray cxposurc rcsult from dircct cllccts.. Th. indircct theort suggcsts that x-ray photons arc absorbed wilhin thc ccll and causc lhc lbnnation oi loxins.\ hich in tum d.rnagc rhc ccll For cxamplc. \'hcn x-ray pholons arc absorbcd by watcr within a ccll. free radi-calforDaiion rcsul1s. Thc iicc radicals combinc to form loxins /s.g, l/r(r. which causc ccllular dysfunction andrro'lrg1. danl3sc. Aboul two{hirds of radiation-induced biological damagc rcsults fiom indircct ctlccls.

I)amag. lo thc DNA molecul is lhc primafv ncchanism fbr radiation induccd cel1 dcirth. nutation, andos response curve is uscd to dcmonslratc thc rcsponsc i/drndgel of(issucs to thc dosc arr?ornr.) ofradiation rc-

cfTects ofradiation can bc classificd as:. Stochastic cftcctsi occur as a direct function of dosri lhc probabilirr" ofoccurrcncc incrcascs \\'iih incrcasingibnrrbcd dose: howeve., lhc sclcrity ofcliccls does not dcpcnd on thc magnitudc ofthc ahsorbcd dose. Exam-rlc\ ofsrochastic cficcls includc cancer r... trrro,-./ induction and genetic m|Itations (i.?., DNA tld"ng.'). \ on sroc h a stic cffects /.le ter ti i\ ti( L'[e. ts)t arc somatic cficcts tha! havc a th reshold and i n creasc in scvcrily$ith increasing absorbcd dosc.Eranrplcs of nonslochaslic eilccts includc erylhcma. oral changes. loss of hair,cararact ibnnation, and dccrcascd fcriility. Importanl When comparcd silh slochastic eflects. nonstochastic cl-fi-cts require Iarger radiaiion doscs to seriously impair hcalth.

.rll cclls rcspond 1r) r:rdidlion in thc samc manncr In general, thc gre.tcr thc rate or potential for mitosis andmorc immsture rhc cclls and tissues are, thc greatcr the sensitiritl or susccplibility to radiation. Cclls that arcincludc blood cclls. immaturc rcproductivc cclls, epithelial cclls, and iroung bonc cclls. Thc ccll thatscositive to radiation is ths small lymphocyrc. Radioresistant cclls includc cclls ofbonc. musclc and ncrvc.composcd ofradioscnsitive cells includc lymphoid tissucs. bone marro$,, tcstcs. and inlcstincs.of rad iorcsista n t tissues includc thc salivary glands. kidncy and liver


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periodofcell injury

periodeffects

related Osteonecrosis ofthe jawperiodontal disease

ofthe above

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reactions /e.g., ioni:dtkr1. .lree rudi(al fornalion) lhal lollo."\, the absorption of radiation occur rap-at thc molecular level. I lonever. varying amounts of time are required fbr these changcs to alter cells and

functions. As a result, the obsenable effects ofradiation are not visible immediately aftq cxposurc.following exposurc, a latnt period occurs. The latent period is the pcriod of time between radiationofsymptoms. It may be short or lonc, depending on the tohl dose olradiation received

amount of time it look to receive the dosc.period ofcell injury fbllo$ s the latent period. Cellular injury may result in cell death. changes in ccll tunc-or abnormal mitosis ofcells-rcovery priod is the last event in the sequcnce ofradialion injury Some cells rccover fioni the radia-ir1jury, especially ifthe radiation is "low level."

eflects ofradiation exposure are additive and rhc damagc that rcmains unrepaired accumulatcs incumulative effects ofrepealed radialion exposure can lead to various serious health problemscarcinogenesis, r|hi.h leuds to r\trious caxilonar, genetit nutatiotis whi.h cdure hirth defets. difler-kinds of lculienia and utdrads).

effects can be classified as cithcr:Shorl-term effects: ellecls ofradiation that appear within minutcs. days, or \r'eeksl associated with largcofradialion absorbed ir1 a short period oltime. These effects are not applicable !o dentistry.Long-1rm effects: effects of radiation that appear aftcr years, decades, or generations; associated with

amounts ofradiation absorbed repeatedly over a long period oftimc- Repeated low levcls ofradiarionare linked to thc induction ofcancer, birth abnormalities, and genctic defects.elTects on rells:

. The cell nucleus is morc sensitive to radiation than the cytoplasm. Damage !o the nucleus allccts thc chro'mosomes con{aining D\A and resuhs in disnlplion ofcell division, \l'hich in tum may lead !o disruprionot cell lirnction or cell death.. lllitotic delay occurs afier irrldiation ofa population ofdividing cells.. Radialion causcs cell death by damaging chromosomcs! preventing successful mitosis and also by appo-sit.s /proNromnted cell de.tth).. Cell recovery involvljs enzymatic repair of sirgle-strardcd brcaks of DNA.

clinical complications that occur in bone following inadiation relate to lhe marked reduction in vascularitythe consequcnt d.crcased capacity oflhc bonc to resist infection. Therc is a strong possibilily that inf'eclionofbone will resuh in a nonhealing \lound if the orrl mucous rtembrancs aQlredd] tomprotniscd b)

breaks do\,'n. This may occur spontaneously or fbllowing a loolh extraclion or denture sore and isn as osteorrdionecrosis,

is morc common in the mandible than in thc maxilla. becausc oflhe richer vascular supplvthe nra\illa and lhc fact that lhe nandible is morc frequently inadialcd. Thc mosl conlmon faclors precipitatingarc pre- and pos!ilradialion extractions lnd periodonta] disease. Note: Damage to lhe blood

/d-f.)ppor_erl /o nen,es, ius(le, eL., predisposes a patient 1o thc developmen! of osteoradionecrosisihe I Hs ofORN arc hypocellu)ar bone. hypovascular tis\ue, and h),poxic tissue and bone

prerent osleoradionccrosis: extract all hopelcss tceth three weeks prior to bcadineck radiation trcattncnl, Ifafler radiolherupy, lhc use ofsystemic antibiolics is recommended. Sonc sludies suggesl hypeftaric

rrealmcnls bcfore and afler lrcaimcnt to reduce the risk ofosleoradionecrosis flrr:r r soncrhd (ontn'ofl'hole t ody irradiation:. When the whole body is exposed to low or moderate doses of radialion. thcre are ch.rracleristic changeskolled the aute rddiation slndtomc) th develop, which are quitc different irom thal secn when a relativelysmall volume oftissue is exposed.. Embryos and fetuses are considerably more radiosensitive than adults bccause mosl embryonic cclls are rel-

atively undifferenliatcd and rapidly mitotic. Prenatal irradiation may lead to dcadr or lo spccific devclopmenlal abnonnalilies depcnding on the stage of developmcnl at the tine of irradialion. \otc: No effccts onen'lbryos or fetuses have been shown from low doses used in denlal rldiography.

somatic effects:. Somatic eflects are those seen in the irradiated individual. The most important are radialion-induccd cancers.. Carcinogenesis:- Radiation-induccd cancers are not distinguishable from cancers produccd by odrer causcs.

- Thc incidence ofleLlkcrnia bther thdn CLL) rises following cxposure ofthe bonc marrow lo radialion- Radiation induced solid canccrs, including in lhe thyroid. brain, and salivary glands. generally appeer 10or more yean aftcr exposure and elevdled risk remai.s for lifetime.- Pcnons younger than 20 ycars ofage are more al risk for solid tumors and leukcmias than adults


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first statement is true; the second statement is falsefirst statement is false; the second statement is truestatements are truestatements are false

38Coplrighi o 201l'2012 Dental Decks

(sec)of the above

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oral cavity is irradiated during the course oftreating radioscnsilivc oral malignant tumors. usually squa-carcinoma. Radiation therapy for malignant lesions in the oral cavity is usually indicated when theis radiosensitiv, Ndvanced, or deeply invasiv and cannot be approached surgically. Fractionation

dose into multiple smalldoses provides greater tumor destruction than would be possible withsingle dosc. Fractionation also allows incrased cellular rpair of Dolmal tissues, \\+ich are believedhavc an iiheritantly grcatcr capacity for recovry than tumor cells. Another vahrc offractionation is that i1mean orygen tension in an inadiated rumor, rendering the turnor cells morc radiosensitive.

effect on oral tissus:. Oral mucous membranes: by the end of the sccond weck ofthempy the mucous mcmbrancs bcgin toshow areas ofrcdness and inflammation (zac.rrr'ti9. As therapy continues. lhe mucous membmne beginsto break down, u,ith the fomation ofa white to yellow pseudomembralne ldesquamated epithelial larcr).At the cnd oftherapy the mucositis is usually most severe, secondary infection by Candida albicans is acommon complication. After inadiation the mucosa bcgins to heal rapidli, and is usually complete byabout 2 months.. Taste buds: arc sensitive to radiation. Therapeutic doses cause extensive degeneration ofnormal histo-logic architccture oftaste buds. Patients often notice a loss oftastc acuity during the second o. third weekofradiotherapy.. Salivary glands: during the first lew weeks ofthenpy thcre is usually marked and progtessive loss ofsali-\'ary secretion. fi extent ofreduced flow is dose-dependent. The mouth becomes dry freloslomldl and ten-der, and swallo$'ing is difliculr and painful. xcrostomia that has persisted belond a year is lcss Iikely toshow significant retum of function. Importrnt: Salivary changcs hav a profound influence on thc oralmicroflora and secondarily on the dentition, often leading to radiation caries.. Teeth: inadiation ofteeth with therapeutic doses during their development severely tetards their growth.\ote: Aduh reeih are vcry resistant to the direct effects ofradiation exposure.. Radiation cariesi is a rampant lonn ofdentaldecay that may occur in patients who have received a courseofradiotherapy. The carious lesions result lronl changes in the salivary glands and saliva, including reducedtlo(. decreased pH. reduced buffering capacity, and increased viscosiLv.. Bone: lhc primary damagc to maturc bone rcsults from radiation-induced damagc to lhe fine vasculature,\\ hrch is normally already sparse in a dense bone such as the mandible. Subsequent to irmdialion lhere maybe a replacement ofnormal marrow with f'atty narrow offibrous connective tissue. ln addition, the endos-reum become atrophic, sho*,ing a lack ofosteoblastic and osteoclastic acti\.ity, an indication ofncrosis.

with which electrons travel from the filament ofthe cathode to the target oftheupon the potential difference between the two electrodes (kilovoltage).turn, has a very important effect on the x-rays produced at the focal spot.

kilovoltage has nothing to do with the number of electrons that compose the streamfrom cathode to anode. The numbr of electrons (vhich determines the quan-is controlled by the temperature of the tungsten filament (mil-

setting). The hotter the filament, the more electrodes are enitted and availableform the electron stream (the x-ra1,tube cut-rent).Inthe x-ray tube the number ofelec-flowing per second is measured in milliamperes. The intensity of x-rays producedparticular kilovoltage depends on that number. Note: Setting the x-ray machine for amilliamperage actually means adjusting the filament temperature to yield the cur-flow indicated. The milliamperage range for dental radiography is 7-15 mA.l. In dental radiography, the quality ofthe x-ray beam is controlled by kVp.2. The kilovoltage range for most dental x-ray rnachines is 65-100 kV.3. Digital units use a range from 8-40 kvp.4. A higher kilovoltage produces x-rays with greater energy Ievels, shorterwavelengths and more penetrating ability.5.To increase film density, you should increase mA, kVp and time. Also, youshould decrease the source-object distance.

Note*,'


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as intenseas intense

times as intensetimes as intense

Decreased densityore latitudeshorter scale of contrast

scale ofcontrast

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Inverse Square Law is stated as follows: The intensity ofan x-ray beam at a given pointinversely proportional to the square ofthe distance from the source ofradiation.Changing the distance between the x-ray tube and the patient thus has a marked

on beam intensity.intensity of an x-ray beam at a given point is dependent on the distance ofthe measur-from the focal spot. The reason for this decrease in intensity frtr,l, il rs ,nversely pro-

is that the x-ray beam spreads out as it moves from the source. The "spread out"less intense.

example, when the PID length is changed from 8 to l6 inches, the sourcelo-film distancedoubled. According to the Inve6e Square Law, the resultant beam is one-fourth as in-PID length is changed from l6 to 8 inches, the source-to-film distance is re-According to the Inverse Square Law, the resultant beam is four times as

following mathematical formula is used to calculate the Inverse Square Law:original intensity = new distance2new intensity original distance':

The intensity ofthe radiation is inversely proportional to the square ofthe dis-The thickness of alumrrr,tm (approxinateb'2 mm) placed n the path ofthe x-ray

reduces the intensity by one-halfis termed the half-value layer. For example, if anbeam is said to have a half-value of4 mm, a thickness of4 mm of aluminum would beto decrease its intensity by one-half. Measuring the half-value layer determines thequality of the beam. The higher the half-value layel the more penetrating the

effect ofa change in kilovoltage is a changc in the penetrating power ofthe x-rays. Incrcasing kilo-reduces subject cont ast (and the longer lhe scdle ofcontt?saJ; decreasing kilovoltagc incrcascscontrast fard rhe shorter lhe scale of conlrasl. A second effect ofan increase in kilovoltage isonly are neu', morc pcnctrating x-rays produced, but morc ofthe less pcnctrating rays which were

produced at the lower kilovoltage are omitted. Remember: Kilovoltagc controls the speed ofelec-kilovoltage influences the x-ray be.m and radiograph by:

. Altering contrast quality ([or patienls v,ilh thick jaws, iro"ase I ilovoltage). Detcrmining the quality ofthe x-rays produced. Detcnninillg the velocity ofthe electrons to the anodcrefers to thc capability ofthe x-ray film to reproduce the distinct outlines ofan objcct, or, ins ords. to how well the smallcst dctails ofan object are reproduced on a dental x-ray. A ccrtain lack

imagc sharpness is prescnt in every dental x-ray. The fuzzy. unclcar area that sunounds a radiographictermcd the penumbra. Thc sha.pness ofa film is influenced by three factors:

. Focal spot siz: the tungsten target ofthc anode senes as a focal spot; this small area convcrts bom-barding electrons into x-ray photons. The focal spot concentrates the electrons and crcatcs an cnor_mous amount ofheat. The size ofthe focal spot ranges from 0.6 mm: to 1.0 mm:and is determinedbt rhe manufacturer ofthe equipment. lmporlant: The smaller the focal spot area, the sharper theinlage appears: the larger the focal spot arca, the greater the loss of imagc sharpness. Fitm composition: sharpness is relative to the size ofthe crystals found in the emulsion. The emul-sion offastcr film contains larger crystals that produce less image sharpness, whcreas slowcr filmcontains smaller crystals that produce more image sharpness.. \Iovement: a loss of image sharpness occurs ifeither the film or the paticnt moves during x-ray cx-posute.

Image sharpness can also be improved by increasing the distance between the focal spot and thcby using a long, open-cndcd cylinder and also by decreasing thc distance betwceil the object andfilm.


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timethe film is a one-film packet or a two-film packel

t2Coptr'glt @ 2011,2012, Denial Decks

Positive anodeNegative anodePositive cathodeNegative cathode

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rcfcrs lo thc ovcralldarkncss r/b/d(izer, ofa radiograph:. Dcnsit_v will increase as mA. kvp, or cxposurc limc is incressed. Dcnsity will decrease as mA, kVp. or cxposurc timc is decreased. Reducing lhc distancc bctwccn thc focal spot and thc film also increases thc dcnsit)thicker thc objcct or thc grcatcr its dcnsity, thc morc thc x-ra] bcam is attcnuatcd and lhc lighter thc rc-

image will bc.oflhe fi1rn Nflcr x-ray cxposurc is cxprcsscd in tcnns ofits optical densit!:

whcrc l0 is thc rnlcnsity ofincidcnt light /e,.a.,/.),r a vi4 rar./ and Ir is thc intcnsity ofthc lighl transmittcd through thc lilm.

roulinc radiogr.phy thc uscful rangc ollilnr dcnsilics is approximatcly 0,j ften light) to 2 l|e^ dort.t. Bcyondthc imagc is usually too light or 1oo dark to bc diagnoslically uscful. Not: ln a \\,cll-cxposcd andradiograph. thc opticaldcnsit_v ofcnamcl is about 0.,1, dcntin is about L0, and soli lissuc 1s about 2.0.

Thc operator ofan x-my unil is in conirol ofthrcc factors:L Kilo\oltage: thc quality or penetrating power ofthc x-ray bcam2.}{illiamperrge: the quantity or numbcr of x-rays produccd*** lncrcasing nrillianrpcragc rcsults in an increase in thc numbcrofx-rays produced and an increase in lhc tcm-

ocralurc of thc filamcnt.3. Exposure time: thc lcngth of time x-rays are produccd and patient is cxposcd to lbcm. ljxposurc tnnc is mcas-urcd in impulses bccausc x-rays arc crcalcd in a scrics ofbursts or pulscs rathcr than a continuous skcam. Oncinrpul\c occurs clcry 1160 ofa second; thcretbrc, 60 impulscs occur in I second.

L Radiographic speed is thc amounl ofradialion rcquircd 1o prodlcc a radiographic tilm ofslandarddcnsir,v. Thc fastcst dcntal film cuncntly availablc is F-spccd.2.Thc film characlcristic thal js ihc rcvcrsc ofcontrast is film latitude. Thc highcr thc contrast. thcsmallcr thc laiitudc and the lowcr thc contrast, thc grcalcr Ihc latiludc. La{itudc is. thercforc, thc rangcofradlation intensitics that a film is capablc ofrccording.l. Radiographic not(le /o/-nrrre) is thc appcarancc ofuncvcn dcns;ty ofan cxposcd radiographic film..l Rrdiographic artifact$ arc dcfccts causcd by cnors in film handling or crrors in film proccssing. ormarks or scratchcs fiom rough handling.5. Sharpness is thc ability ofan x-ray lo dcfinc an cdgc prcciscly.6. Rcsolulion. or rcsolving powcr, is thc ability ofan x-ray to rccord scparalc structurcs that a.c closclogcthcr.

r-ral tubehead is a tighlly scalcd. hcavy mctal housing that conlains thc x-ray tubc thal produccs dcnlal x-ray!.pans ofthc tubchcad includc the following:. Ntetal housing: is thc mctal body oflhc tubchcad lhat sunounds ihc x'ray tubc and transfonncrs and is iillcd \lithoil: it prolccts thc x ray tube and grounds thc hiSh-voltagc componcnts.Insulating oil: ;s thc oil tha! srmounds thc x-ray tubc and transformcrs insidc thc lubchcadi it prcvents ovcrhcatingby absorbing thc heat crcalcd by thc produclion ofx-rays'Tubeherd seal: or thc aluminum or lcadcd glass covcring thc tubchcad that pcrmits lhc cxil ofx-rays lionl thctubchcadt it scals lhc oil rn lhc tubchcad and acts as a flltcr to Ihc x'ray bcam. X-ray tube: is thc hcart ofthc x-ray gcncrating systcm. Transformer: is thc dclicc that altcrs thc voltagc ofincoming clcctricilv. Aluminum di$ksl shccts of0.5-mn thick alurninum placcd in thc path ofthc x-ray bcaml they filtcr out non'pcnctrating, longcr wavclcngth x-mys. Lead collimator: is a lcad platc wilb a central holc that fits dirccily ovcr thc opcning ofdrc mcial housing whcrcthc x-rays cxit; ii rcstricts lhc sizc ofthe x-ray beam. Position-indic:rting device (PID)r is an opcn'cndcd. lcad-lincd cylindcr that cxtends from thc opcning ofthcmctal housing ofthc tubchcad; it aims and shapcs thc x-ray beam

tube is thc hcarl ofthc x-ray gcncrating systcm. It consists ofa lead-glass housing, a negative cathode,a positive rnode. Electrons arc produccd in thc cathode and acceleratcd toward thc anodc; thc anode con\cr(s

into x-ravs.. l,eaded-glass housing: is a leaded-glass vacumm tubc that prevents x-rays liom cscaping in all dircclions. Oncccnlral arca ofthe ieadcd-glass tubc has a "window" that pcrmils lhc x-ray bcam lo cxit the lubc aDd directs lhex-ray bcan toward thc aluminum disks, collimator and PID.. Cathodc /r/ rgdrtrt, r1e. rftr.L,/: consists ofa tungsten wire lilament in a cup-shapcd holdct nradc of molyb-denum. The purposc oflhc calhodc is to supply the electrons nccsssary to gcncralc x-rays. Thc clcclrons produced in rhc nega(i!e cathodc arc accclcratcd loward thc posjlivc anodc. Thc cathode includcs thc ibllorling:. Tungsten filament: is a coilcd wirc madc oftungstcn. which produccs clcctrons \vhcn heatcd.llollbdenum cup: tbcuscs thc clcctrons into a narro$,bcam and dirccts thc bcam across thc tube lo*,ard drc

tungstcn targcl ofthe anode. ^node (ot poriti\,t ?l?(rod4r consisls ofa waftr-thin tungstcn platc cmbcddc'd in a solid coppcr cord. Thc pw'pose oithe anode is to convert elcct.ons into x-ray photons. The anodc inludcs thc following. Tungsten target: scrvs as a focal spol and convcrts bombarding clectrons into x-ray photons. Copper stem: funclions to dissipatc thc hcat away from thc tungstcn largct

D = log l0 (lo.l1)

Notc.


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stem

cup

44Coplrighr O 201 I -2012 - Dntal Drcks

neutral atom without a nucleusatom with equal numbers ofprotons and electrons

neutral atom that loses an electron and becomes a positive ionofthe above

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arc gencratcd whcn a srrcam ot clcctrons (\'hkh are prod ed hr rre /i/drrertl tra\cls from thc calhodc toond is suddcnlr- stoppcd by its impact on thc tungslcn larscl. Thc filancnt locrlcd in rhe carhodc is nradcNirc Thc smallarca on thc targcl that thc clcclrons strikc is callcd drc focal spot -il is lhc source of \-L Thc sizc of thc fbcal spol directly influences thc x-nty dcfinition: thc larger the focal spot. thc\oles greair rhe loss nfdcfin:(ion and r\c greater lhe lo\r oI rhc .hartnc.. ol lhc imalc: Copper rs uscd Io hous!' thc anodc bccausc it is a good thcrmal conduclor. dissipating hcat tiom thc

tungstcn krgct and rcducing thc risk ofrnclring lhc largct-

ReFinrcd ti.m Haring. Joen Ia.-nuc.i and l-lura Ja.rn: DentalRxdioErdy Princlties rnd Tec|'.\ue\: lhinl Ldilron O 1000.$nh t.nnss.n ftonr Flsc\icr

Refrinted no'n Haring..roen lrnnuccr trnd Laura J.nsen Denhl Rtdrgrdphl: tnncrples ardTechniqoes: Ihid ldiron '! 1000.wirh pennr$io. from FheYler.

is anything lhat occupics spacc and has mass; rlhcn mattcr is altcrcd, energy rcsulls. Thc indamcntal unilis thc atom. Thc atom consists oal\vo parls:. A ccntral nuclus: is composcd of protons and neutrons. Protons carry positiv clcctnc!l chargcs, !{hcrcasncutrons cary no clcctrical chargc and arc slightly hcavicr than lhc proton. Orbitin8 electrons: arc t;ny negatively chargcd particlcs ihal havc vcry little mass; rn clcctron wcrghs approx-imatcly 1/1800 as much as a prolon orncutron. Elcctrons rravcl around thc nuclcus in $cl1-dcllncd paths known

as orbits or shellsatom contaiis a maximum ofsevcn shclls, cach localcd at a spccific distanc lion1lhc nuclcus and rcprescrtrng

cncrgy lcvcls. Thc shclls arc dcsignatcd wift lhe lclters K, L. N{, N, O, P and Q; thc K shell is locatcd clos'nucleus and has $c highestenergy level. Elccrrons arc maintaincd in thcir orbits by thc electrostalic forceJ

bclwccn thc posilivc nuclcus and thc ncgativc clcctrons. This is known as ihc binding energy ofan clcc-arc capablc ofconibining wilh cach olhcr 1o lbrm molcculcs.

atom conlains an cqual numbcr of protons (posi!i,e Lharyes) ]nd electrons /neg.?/a'. .rr4i.'.!/. An atornan incomplclcly Ullcd outcr shcll is clcctrically unbalanccd and aiicmpls 1o capturc an clcclton from an adjaccniAn aton that gains or loscs an clcclron and bccomes electrically unbalarccd is known as an ion. Ionization jsproducrion ofions. or thc proccss ofconvcning an elom inlo ions. Ionizalion dcals \\'ith electrons only and rcquircs

encrgy ro ovcrcomc thc electrostatic lbrcc that binds thc clcctron to the nuclcus.is capable ofproducing ions and can bc classificd inlo two groups:

. Particulate radiationr arc iiny particlcs ofmattcr that posscss mdss and lra!cl in straight lincs and al high spccds.Thcrc arc lbur typcs:

. llfectrons: can bc class classificd as beta particle. lldst nnring ?l.cttotlj eniuetl lon the tt (k'tts ol rd-dioactir. otonts) ot c thode rays (strcams ol hi!:h-spe.l ek'( trcDs thut origindte in an .\ tut nh.). Alpha particles: arc cniltcd from thc nuclci ofheavy mctals and cxisl as t\\'o protons and nculrcns. $ith-out clcclrons. Protonsi arc accclcrated paniclcs. spccifically hydrogcn nuclci, with a nlass of I and a chargc of+l. Neutrons: are accclcratcd pariiclcs with a mass of I and no clectrical chargc

. Electromagnetic radiation: can bc dcfined as lhc propagation ofwarc-likc cncrg)" /r'rrorlr l,alltr./ through spaccor mattct Illcctromagnctic radiations arc manmade, or occur nah.rrally;cxamflcs includc coirnic rr] \ camma ruyJ,x-r!!-s, UV rays. visiblc light. infrarcd light, radar $avcs, nicro$avcs, and radio wavcs. Thc particle concept(Q d,1tun l2orr) .haructcrizcs clcctromagnctic mdiations as discrctc bundics ofcncrg-v called photons or quanta,Thc wave concept characterizes cleckomagnctic radialion as lvavcs and focuses on thc propenies ofvelocit]'.$avclcnglh. and frcqucncy.


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first statement is true; the second statement is falsefirst statement is falsej the second statement is truestatements are truestatements are false

a6Coptright ,O 20 I 1,20 | ? , Denial Decks

Which of the following occurs only at 70kVp or higher and accounts for a verysmall part ofthe x-rays produced in the dental x-rry machin?

scatter

(Bremsstahlung) radiationradiation

47CopFighr O 201 l'2012' Dental Decks


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is thc encrgy that is uscd (o make x-rays. Electrical encrgv consists ofa flow ofclcctrons through a con-flo$'is known as thc clcctric currcn(. The clcctric currcnr is tcnned direct currcnt frcl whcn thc clcc-flo$,in one direction through lbc co duclor Thc lcnn alternating current /-,14) dcscnbes a currcnt ;n whichelcctrons flow in tl4o opposite dircctions. Rectitication is thc convcrsion otaltcmatiig currcnt lo dircct currentiacts as r self-rectificr ir that it changcs AC irto DC \r'hilc producing x'rays. This cnsrLrcs thatcurrent is alwa]s flor}ing in thc samc dircclion, morc spccilically, liom cathode to anode.

is thc rncasurcncDl ofthc number ofelectrons nroving through a conductor Current is measu.cd in am-or milliamperes /rr,.1/. l'oltage is the meas rcment ofelectrical force thal causcs clcctrors lo movc fron a ncg-pole to a posili\'e oDc. Voltagc is measured in volts or kilovolts /krr. Note: ID thc produclion ofx-rays. bofi thc

and volfagc can bc adjuslcd on thc contfil pancl (mA aditstDrctt dnd kI? adiusttrcrt s\\itthes).is a palh of clcctrica I currcnt. Two electrical circuits arc uscd in lhc production ofx-rays:a lolrrvoltagefilamcnt circuil and a high-voltage circuit. Thc Iilament circuit uscs J to 5 volts. regulatcs thc llo\\, ofclcckical

to thc filament ofthc x-ray tubc, and is controllcd by thc milliampere settings. Thc high-r'oltage circuit65.000-100.000 ! olts. providcs thc high voltagc rcquircd lo accclcratc clcctrons and to gencratc x-rays in thc x-tubc, and is conlrollcd by thc lilovoltage settings.is a dcvjcc that is uscd to cithcr incrcasc or dccrcasc lhc vollagc in an clcctrical circuil. Transfbrncrs

thc \oltagc ofthc incoming eleckical currcnt and then routc lhc cleckical cncfgy to thc x-ray tubc. In lhc pro-ofdcntal x-ra)'s, thrce transfbrmers arc used to adjusl lhc clcctrical circuils:. Step-down transformcr: is uscd to dccrcasc thc vollagc fiom thc inconring I l0 or 220 line voltage to the 3 to5 \ ohs rcauircd. Step-up transformer: is used to inc.casc the voltag from the I l0 or 220 linc roltagc lo thc 65,000 to 100.000\0lts rcquired. Auto-transformer: scn,cs as a voltagc compcnsator that corrccis for miror flu!tuations in the currcnlI Thc milliamperage f/r,.|.) or tube current swltch on thc control panel regulates thc tempcr.tura of\ot{* th filament and thus thc number ofelectrons emitted,2.Tube current or mA controls thc numbcr ofphotons gclcratcd //,rlersitt ol the bru , but rot thc

beam cncrgy. Thc quantity of radiation produccd by an x ray tubc is dircctly proponional 1o lhc tubc cur-rcnt /rr.,1/ cxposurc timc.L Thc livp control sclccts voltage from diftcrenl levels on thc autotransformcr and applies it across Ihcprimary winding ofthc slcp-up transtbrmcr,+. In dcntal x rays, the qualit) ofthe r-ray beam is controllcd by kvp.5. Thc cflcct ofchanging timc is sinply 1l) control thc "quanlily" ofthe ex?osutc (the nunbcr ol pho-Iotts sencratel).

all x-ra)s produccd in thc x-ray lubc arc thc same; x-rays rlilltr in energy and wavclength Th cnergy andofx-ravs varies bascd on how the clcctrons intcract wilh thc tu'rgstcn atonrs in lhe anodc. Thc kinctic cnof rhc clcctrcns is converted to x-ray pholons via onc oft$o mcchanisns:. Gene.^l (Rrcnsstrfihnrg or braking radiation: a fomi ofradialion lhat occurs lrhcn speeding clcctrons areslosed bccausc ofihcir intcraclions with thc nuclei oftarget alofis. Thc tcmr braking radiation, rcLrs to thc sud-den stoppnrg or slowing ofhigh-speed eleclrons hitling the tarSet in thc anodc. Most x-rays arc produccd in lhisnlanner; lpprorimately 707o ofthc x-ray cncrgy produced at thc anodc can be classificd as gcncral radiation. Charactcristic radiationr is produccd wien a high-spccd clcctron dislodgcs an inncr shell elcctron liom thctungslcn alonl and causcs ionization ofthat atom. This tlpc ofradiation accounts for a vert-' small part oi x raysproduced in thc dcntal x-ray nrachinc and occurs only at 70 kvp and abovc bccausc thc binding cncrgy oflhc Kshcll .lcctron is approxirnatcly 70 kcv

radiation refcrs to lhc pcnctrating x-ray bcam that is produccd at lhe llrrgcl oflhc anode and cxjls thc lubcTlij \,rr] beam is olicn rcfcrrcd to as thc primary bcam or useful beam.r!diation reicrs to x-radialion that is crc.rtcd whcn thc primary bcam inlcracls u'ith mattcr li tl tal rd'].t,rp/l.krutoitklud(skesolitissu(softheheud,thehotrcsolth"skull,adtheteeth).NoteiSccondaryislesslhan primary radialion.

is onc ofrhc intcracrions ofx-radialion rvith mattcr in which thc path ofan x-ray pholon is altcrcd'ran cr $ ith ou t a c h,lngc in cncrly. Cohcrcnt scattcr accounts for 8 o/" of t hc inicractions of mattcr with thc dcnia I

scatter is onc ofthe intcractions olx-radiation with matter in which thc x-ray photon is dcllcctcd from itsand loses cnergy. (lomplom scaitcr accounts ibr 6270 ofihc scaitcr that occurs in diagnostic radiography

is onc ofthe intcractions ofx-radjation \\'ith mattcr, 3n x-ray photon intcracb with an or'.1cctron, and all of the cnerg! of the photon is absorbed by thc displaccd clcclron in thc form of kinctic en-Thrs accounts for 307o oflhc inlcractions ofmattelwith lhc dcntal x-ray bcam.

the qurntily ofrudiation exposufc or dosc is tcrmcd "dosimetr).". Erposure: is a measurc ofradiation quantily, the capacily of thc radiation to ionizc uir Thc roentgcn /Rl is thctradilional unil ofradiation exposurc mcasurcd in arr. A bsorbed dose: is a m casurc o f enerey impartcd by any typc of ionizing radiatbn 1o a nass of any typc of matltcr Thc SI unit is thc gr"d-r, (Gy). thc tradilional unit is lhe /ad. Effective dosc: is uscd to cstimalc lhc risk in humars. Thc unil ofcfteclive dose is thc Str'r'l?,'/ (Sv). Radioactiritr: is thc decav ratc ofradioactivc matcriai. The unit is thc 8c(quercl(Bq)


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All ofthe following rre components of inherent liltration EXCEPT one.Which one is the EXCEPIIOM

glass windowleaded cone

seal

48Copyright O 201 l-20 | 2 - Dental Decks

Rad Protection

Man has always been exposed to natural radiation arising from the earth aswell as from outside the arth. The radiation we recive from outer space iscalled terrestrial radiation or terrestrial rays.We afso receive exposure from man-made (artificial) radiation, such as x-rays,radiation used to diagnose diseases and for cancer therapy.

The first statement is true; the second statement is lalsehe first statement is false; the second statement is trueoth statements are true

statements are false

49Cop)rlghr C 20ll 20ll, Denral Decks


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are two types of filtration used in the dental x-ray tubehead:. Inherent filtration: takes place when the primary beam passes through the glasswindow of the x-ray tube, the insulating oil, and the tubehead seal. The inherent fil-tration of the dental x-ray machine is equivalent to approximately 0.5 to 1.0 tnm ofaluminum.. Added filtration: refers to the placement of aluminum disks in the path ofthe x-raybeam between the collimator and the tubehead seal in the dental x-ray machine. Thepurpose of the aluminum disks is to filter out the longer wavelength, low-energy x-rays from the x-ray beam. The low-energy, longer wavelength x-rays are harmful to thepatient and are not useful in diagnostic radiography.total filtration ofthe x-ray beam before it reaches the patient consists of the inher-filtration plus the added filtration. Important: Govemment regulations require total

to be equal to the equivalent of 1.5 mm of aluminum for up to 70 kVp and 2.5of aluminum for higher voltages., . .. l. Longer wavefength x-rays (those produced ut lower kilovollages) are eas-ily atrsorbed.2. Shorter wavelength x-rays (those produced at higher kilovoltages) pene-trate objects more rcadlly (the!-Jbt"m the image on theJilm).

3. Filtration of the x-ray beam results in a higher energy and a more penetr-ating useful beam. Filtration reduces patient dose, decreases contrast and in-crass the density of film.

The x-ray beam is composed ofrays ofdifferent wavelengths and penetrat-po*er (the tern used Jbr this is polychromatic) because the potential across the tubeconstantly as the voltage varies.

The radiation wc rcceive liom outer space is called cosmic radiation or cosmic rays.of radiation exposure:. Naturaf r:rdiation /rackgrourul rarliation)t is by f'ar the largest contributor (8J%) to the radiafion expo-sufe ofpeople living in thc U.S. today. Background radiation, resulting fiom extemal and intemal sources,vrelds an a\erage annual E ofabout 3 msv.

- Erternal: exposure in this category is due to cosmic and terrestrial (/iom lie rolll rtdiation or that orig-inaling in thc cnvironment. These sources contribute about l670 ofthe radiation exposure lo lhe popula-tion.- Internal: sources ofintemal radiation include inhaled mdon fi6z,, and ingested radionuclides 111%/.

. ArtificiAl radiation lnan-made radiation)i Ihese may be categorized into tbree major groups -medicaldiagnosis and treatmcnr (11%, of rJhich dental x-ray examinations are rcspottsible for only 2,5% ofthkalerage a ual t-ru! diagnosrt etporrle/, consumer and industnal products and sources d9'o/, and nuclearmedicine f4?ir. Artificial radiation yields an average annual E ofaboul0.60 mSv or l77o ofthe annual ra-diation exposure !o the U.S. population.protection standards dictate the maximum dose ofradiation that an individual can receive. Thc max-permissibl dose /MPD./ is defined by the N^tional Council on Radiation Protection and Measurements

as the maximum dose equivalent that a body is pelmifted to receive in a specific period oftime. Theis the dose ofradiation that the body can endure with little or no injury Important: The yearly MPD

a non-occupationally exposcd person is 0.1 rem/year (.0001 Sv/year). The yearly MPD for occupation-cxposcd pcrsons, or persons who work with radiation, is 5.0 rem/year (0.05 Sv,/year). The IUPD for ane!posed pregnant woman is the same as that for a nonoccupationally exposed pcrson, or 0.1(.0001 Svlyear).

dose in radiography: The goal ofradiatiorl protectjon procedures is to minimize the exposureofllce perconnel and patients during the radiographic examination. The philosophy ofradiation protectionused in practice today is based on the principles ofALAR{ (As Low As Reasonabb' Ac hierah le ).

The primary risk from dental radiogEphy is radiation-induced cancer. Although the risk involved withradiography is extremely small in comparison with other risks such as smoking or consumption of fattybrsis exists to assume that it is zero.


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first statement is true; the second statement is falsefirst statement is false; the second statement is truestatements are truestatements are false

50Cop)right O 201l-2012 - Dntal Decks

placement

5tCoplriSht O 201l-2012 ' Dmtal Decls


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ofthe lbllowing reduce the amount ofradiation to thc patient:Lead aprons and collars. Lcaded thyroid collars are recommendcd in individuals undcr 30 years ofage.

statcs mandate lhe use ofa lead apron on all patients.Increased flhmtion using an aluminum diskUse E-speed film. F-spced fitm or digiral imaging for pcriapical and bite$ing radiographsLead diaphragms placcd within the cone ofan x-ray tubehcadCollimating an x-ray beam: using a rctangular collimator siSnificandy reduces patlenl exposureUsing a long 116 ircl, PID is prclcrrcd because it produces less divcrgence oflhe x-ray beam. By doing

)ou are increasing the source-film distance and rcducing patient exposurc as \r'cll as inlproving imagcThe use of rrre earth intensifying screens for all panoramic and cephrlomctric radiographyFrlrn-holding devices are also eflective in reducing a patient's exposufe to x-radistionE\posure iactor seleciion also limits the amount ofx-radiation cxposure reccivcd by thc patient The den-

can control thc cxposure factorsby adjusdng thc kilovoltage peak, milliamperage. and dre timeon thc control panel ofthc dcnlal x-ray machine. Note: On some machines the kvp peak and orAare presct by the manufacturff and cannot be adjusted.- \ .cI'irg of ?0 lo c0 k\ p lecn. nalicnls cxf'osure ro 3 mitrimum- Scr m'\ value to highst possible value ifvariablc. Iligher mn sefiings produce a beam \\ ith morc crl-ergt and increasc the intensity ofthe x-ray beam.- \diust exposure time to achieve optimum densityImportant: nrA and exposure time are inversely relatcd. \lllen altering mA, the exposure time nust

bc adiusred to maintain diagnoslic density ofa film.protectioni Radiation exposure to the opcralor can be reduced by standing at least six feet a\\'ay,

a l.ed shield, or bolh when exposiDg diographs. The operator should never remain in lhe room hold-:-:: \-.3\ packcl irl place tbr the palicnt. If a film must be held in place by someonc else (/br d clliki).:h.' f,rr.nI and havc him or her hold rhe film. AII dental personnel should lvcar film badgcs thal moniiorlloiages. \otei The opemtor must avoid the primary x-ray beam by positioning lhemselves at a 90degree angle ro ihe beam.R:sarding the taking and processing of dentr I radiographs, al$ays remcmber!o maintain propr in-

/appl.l tniverssl prccauliohs) at all tims!:!

the x-ray tubehead a collimator (leatl plate \4ith a hole in the middlel is uscd to restrict the size andofthe x-ray bea . A collimator may have either a round or rectangular opcniDE.

. A rectangular collimator resfficts the size ofthe x-ray beam to an area slightly iarger than a sizc 2InrrdL,ral film anJ \rgnificantll rcduccs paticnl c\lo\urc. A circular collimator produces a cone-shaped beam that is ?.75 inchcs /7 czrl in diameler, consid-erabJy Iargcr than a size 2 intraoral film. Important: wtcn using a circular collimator. fcdcral regu-lations require that thc x-ray beam be collimated to a diameter of no more than 2.75 inches 17 cD,as it exits from the PID and rcaches thc skin ofthe patient.

positioning-indicating device /P1Dl, or cone. is uscd to dircct thc x-ray beam. Therc are three basicofPlDs:. Conical: appears as a closed. pointed plastic cone. Wlen x-rays exit from the pointed cone, they pen-etmte the plastic and produce scatler radiation. To climinatc cone-produced scattct radiation. theconrcal PID r\ no longer used in dcnliqlrv.. Open ended and lead-lined rectangular or round PIDs: arc uscd that do not producc scatter tadia-tion. Both rectangular and round PIDS are commonly available in n\,o lcngths:. Short /8-i,r.r,. Long (16-inch)*** Thc long PID is preferred because less divergence of the x-ray bcam occlrrs. Of the threer-vpes of PlDs. the rectangular type is most effective in rcducing patient exposurc.

do not reduce thc amount of radiation rcceivcd by thc exposed tissucs. but reduce thctissues duc to x-ray bcam divcrgcncc.

The x-ray beam consists ofmany different $'avelengths. The short w.velength (high en-rays have great penetrating powcr; long wavelength flox,erergl, rays have low pcnctrating po\r'ernot rench ihe fiJm in reasonable quantitics since thcy are atlenuated by the soft tissues. Low en-

rays add only to thc total amount ofradiation the patient receives. Aluminum discs are used to fil-useless long wave rays. increasing the overall quality ofthe beam.


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The film is bentThe film is placed backwards in the mouth

improper vertical angulation is usedimproper horizontal angulation is used

Source-film distanceFilm-object distanceFocal spot sizeCentral ray directionFilm parallelism

52CoDright O20ll-2012 - Dental Dck

Copright O 201l-2012 - Dnbl Deck


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Figure #1. A rcversed film appcarslight lvith a hcrringbonc cfiect.

.rlr thol(ri refnnred fionr Hlrlng- Joc.lannuccr and Laura J.nsen: DerialRadiography: Iri.ciples.nd Te.hniques:Ihrd F.dilion O :000..ennjrion liom Elsevier

rules for accurate image formation when taking x-rays:l. Use the smallest focal spot that is practical.Note: The size ofthe focal spot influences radiographic definition or sharpness. Theyare inversely proportional. The operator cannot control the size ofthe focal spot.2. Use the longest source-film distance that is practical in the panicular situation.i. Place the film as close as possible to the structure being radiographed.J. Direct the central ray at as close to a right angle to the film as anatomical structuresll ill allorv.5. As far as is practical. keep the film parallel to the structure being radiographed.

Figure #3. Thc bcnt tilm appcars distorted.

t_igure #2. The film dcmonstrates a doublc cxposure. Figure #4. Movcmcnt rcsulls in a blurred image.


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RADIOLOGY Tech

A periapical of the left maxillary canine shows an elongated tooth whichdoes not capture the apex of the canine. \yhile taking the periapicalof the left maxillary canine, the operator had an:

ncorrect horizontal angulationncorrect vertical angulation

ofthe above

54Copyrighr C 20ll l0ll Denlal Decks

RADIOLOGY Tech

The two radiographs below were taken with the buccal object rule inmind, In film #2, the x-ray tube was directed from a mesial angulation.What is the spacial position of the circular object in these radiographs?

The object lies lingual to the first molarThe object lies buccal to the first molarThe object lies between the second premolar and the first molarThe object lies directly apical to the first molar

Film #l 55 Film #2Copyright C:01l -1012 - Dental Decks


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is directing x-rays so that they pass vertically through the part being examined.is accomplishcd by positioning thc tubchcad and direction ofthc ccntral ray in an up-and-(vertical) planc. lmportant: Foreshortening (See fgurc #1) rcfcrs to a shortcncd imagcelongation /Seefgzrc #2) refers to an elongated image. Both are produced by an incorrect ver-angulation. Excessive vertical angulation causes foreshortened images, while insullicient

angulation causcs clongatcd images.

#1. If the verticalis too stccp. thc

a.c foreshoracned.Figure #2. Ifthe venicalangulation is too flat. thcimagcs arc elongatcd.

Borh phoros rerrinred fromHlnng, Joen Iannucci andLaun J$sn: DenraL Radioela-phy: Principles and Tcchniqueslftnd Ednion. O 1000, rvilhI)emission frcm Eh.vi.r

is maintaining the central ray at 0 degrees as the tube is n]oved around theThis is accomplished by positioning the tubehead and direction ofthe central ray in a side-(horizotlt.il) plane. r-ote: The general rule for horizontal angulation is that the central ray

be perpendicular to the mean antcropostcrior plane ofthe teeth being x-rayed.horizontal tube angulation causes overlapping (teeth images are superim-

on eaclt otlrcr).central ray is said to be at 0 degrees when the x-ray tube is adjusted so that the central ray is

to the floor Ifthe tubehead is directed at the floor, it is called positive angulation; ifit isthe cciling. it is called negative angulation.

buccaf objct rule falso called the tube shili technique) is used to determine an ob-spatial position within the jaws. This technique utilizes two radiographs of an ob-exposed with slightly different tube angulations. It then compares the object's position

the radiograph with respect to a rferenc point (e.g., /re root of a tooth,/.the tube is shifted and directed from a more mesial direction, and the object in

appears to have moved mesially with respect to the reference point, then the ob-Iies lingual to that reference point. Conversely, ifthe tube is shifted mesially and thein question moves distally, it lies on the buccal aspect ofthe reference object.

the acronym SLIQB -+ $ame-!ingual, Qpposite-guccal.Ilthe object in question appears to move in the same direction as the x-ray tube, it

on the lingual aspect. lfit appears to move in the opposite direction as the x-ray tube,is on the buccal aspect.


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Tech

After developing her bitewings, a dntist realizes that she has too muchoverlap t etween the contacts of adjacent teeth. This is an error caused by:

vertical angulationlittle vertical

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